The research project was set up by Michael Barrus and Catharine Winstanley to investigate addictive behaviours. The ‘rat casino’ was designed to teach the rodents to gamble in order to win sugary rewards, but the rats were given a choice between four different levels of risk. If a gamble succeeded, the sweet reward was given immediately, but if the gamble was lost, the rodent was punished with a period of time out.
The four risk options allowed the rats to choose from a high-risk, high-reward opportunity down to a low-risk, low-reward opportunity, and the rodents – clever creatures that they are – quickly learned that the most advantageous approach was to go for smaller rewards and win more often.
The researchers then decided to add external stimuli in the form of flashing lights and attractive sounds whenever a gamble was landed. The bigger the win, the more light and sound the rats were exposed to as a kind of audio-visual reward to accompany the sugary treat that was landed. Whilst the scientists had expected these stimuli to increase engagement of the rats, they were surprised to discover that the rodents soon changed their previous approach quite dramatically.
With the lights and sound in place, the rats abandoned their ‘modest risk for modest rewards’ approach and instead began to pursue the higher risk options in order to experience the more intense audio-visual celebrations. When the researchers then administered a drug that increased the amount of dopamine that could be received by the pleasure centres of the rat’s brains, those high-risk behaviours increased. However, when another drug which inhibited dopamine receptors was administered, the rodents reverted to their original low-risk approach to the gambling opportunities.
Whilst the investigation into the role that dopamine plays in addictive behaviours will continue for some time to come, it is notable that the influence of external stimulus on gambling behaviour has now been scientifically established. Of course, casino operators have intuitively known about this influence for decades, which is probably why the slot machines that tend to get the most attention at both bricks-and-mortar and online casinos are the ones that flash the brightest and jingle the loudest.